Thread miller



Oct. 19, 1948.

F. J. KRATCHMAN THREAD MILLER Filed Sept. 22, 1944 2 Sheets-Sheet 1 llll ,lllllllllllll Illu;

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Oct. 19, 1948. F. J. KRATCHMAN 2,451,497

THREAD MILLER Filed Sept. 22, 1944 y 2 Sheets-Sheet 2 4 INVENTOR FREDERCK J. KRATCHHAN; BY e Patented Oct. 19, 1948 UNITED STATES PATENT oFF-ICE 8 Claims.

(Granted under the act of amended April 30, 1928;

This invention relates to a thread miller and has for an object to provide an improved thread miller intended particularly for milling internal buttress threads for armor bolts.

A further object of this invention is to provide a thread miller particularly useful in quickly providing internal threads in armor plate as compared to the previous practice of making such threads by using a succession of taps. With the previous method it was necessary to undercut the bottom of hole to provide for chip and tap clearance and to use about six successively sized taps in making internal buttress threads in armor plate for a bolt. Such previous method would take about an hour per thread. With the present device the need for the taps and undercutting is eliminated and the thread is provided in a considerably shorter period of time.

A further object of this invention is to provide a thread miller which utilizes a carbide tipped cutter which results in higher productionand, in addition, it conserves strategic high tungsten bearing tool steels.

A further object of this invention is to provide a thread miller to produce any combination of thread form, pitch, diameter, and depth desired in internally threaded holes which may be used either with a radial drill press of the type found in many machine shops and may likewisel be used with a portable drill head permitting the work to be performed in any convenient place, even when the armor plate may already be in position on a ship or other vehicle.

With the foregoing and other objects in view, the invention consists in the construction, combination and arrangement of parts hereinafter described and illustrated in the drawings in which:

Fig. 1 is a partly sectional and partly elevational view of the thread miller.

Fig. 2 is a sectional view on line 2 2 of Fig. 1.

Fig. 3 is a sectional view on line 3-3 of Fig. 1.

Fig. 4 is an elevational view of the carbide tipped cutter, and

Fig. 5 is a sectional view on line l5--5 of Fig. 4.

There is shown at I the thread miller of vthis invention in the position in which it has just completed milling a thread II in a piece of armor plate I2, the thread II having been milled in the sides of a previously drilled cylindrical hole, the milling having commenced at the bottom I3 of the drilled hole and having finished at the surface of the plate I2 providing ample space for chip accumulation. The thread miller I 0 includes outer housing I4 provided at its upper end with a split ring I for securing the same by means of the socket head screws I6 to a drill press.

Cooperating with the drill press spindle I'I isl a taper sleeve adapter I8 which is' internally splined to cooperate with the external splines (Cl. SiO-11.58)

March 3, 1883, as 370 0. G. 757) of a splined drive shaft 2l. Thesplines 20 of this drive shaft 2l are journalled in the bushing 22 within a bearing 23 whose `outer raceV 24is supported on the upper edge of a supporting sleeve 25, which supporting sleeve25 rests in turn on an internal shoulder 26.. Threaded on the drive shaft 2l as at 2l is the upper race 23 of a thrust bearing 30 having a lower race 3| supported in a recessed neck formed in the top of a drive shaft sleeve bearing 3.2 and securing this sleeve bearing against a ilange 33 on the .lower end of drive shaft 2 I. Secured on the sleeve bearing 32 by thread 34 and circular nut 35 is an inner housing 36v Whose upper portion 3l is .provided with an acme interrupted thread33 which terminates in a cylindrical portion 39.

`This cylindrical portion 39 is provided with ,a radial slot 40 extending 180 thereabout, below which it is joined to an internally eccentric lower portion 4I. The interrupted thread 88 of the upper portion 3l of housing 36 is made in two sectors separated by 90 cylindrical portions 42, as will be apparent from Fig. 2. Cooperating with the interrupted thread 38 and interrupted portions 42 is a worm wheel 43 having corresponding internal cylindrical portions andan eX- ternal thread 44 meshed with a spiral threadli on a worm shaft 46. l Y

The Worm shaft 4S is journalled in suitable bearings 4l and 48-in a boss 50 formed on the side oi' the outer housing I4. The worm shaft 4S is -rotatable by means of a handwheel ior manual operation, although obviously'thehandwheel 50 could have a power connection sub stituted therefor. The worm wheel 43 is heldin position on top of a lead screw guide nutI which is threadably secured as at 52 by yan interrupted external thread, engaged in like manner with a (zo-operating internal interruptedy thread in the lower end of outer housing I4, permitting rapid removal of entire inner housing 35. By disengagement of taper sleeve adapter I8 from drill press spindle I'l, it is possible to insert appropriate hole producing tools in preparation to thread milling without thel necessity of removing the `outer housing. ThisV lead screw guide nut 5I is provided with an internal acme thread-53 eX- tending continuously around its inner wall-from the` top edge to a point -54 somewhat above its bottom edge. .When the handwheel 50 is rotated, the worm shaft 4-6 causes the worm wheel 43 to rotate,. thereby causing -the inner housing 36 to rotate. As the inner housing 36 rotates its interrupted thread 33 meshes with theinternal thread 53y of the guide nut 5I thus causing the inner housing 36 to rotate in a spiral path determined by these cooperating threads.

Extending through the eccentric inner portion 4I of the inner housingv 36 is an adjustable eccentric bushing 55. The bushing 55 is provided with `62 cooperating with a `of shaft 58 to secure it more j ing from the control l a 180 annular groove VIII of housing 36 is provided with s eccentricity of cutter shaft 58, and

operation, the lock collar 1I `is preset by means ofjits set'screws-at -such'a position that rotation of Control collar liluntil stop pin 68 engages lock 12 will result in the exact desired degree oi the exact desired depth of thread.

to the cutter shaft 58 while the eccentricity of cutter shaft 58 is being variedas well as while it is being maintained. On the lower end of the drive shaft 5B is secured a cutter 6I by meanso a stud screw 62. The cutter 6I asshown in Figs.

4 and 5 may be provided with a .hexagonal-recess I similarly shaped end 83 iirmly thereto. The cutter 6I may be provided with a plurality of iiutes 64 which are tipped withv carbide as at 65 as shown. f The relative eccentricity oi the shaft 58 is controlled by rotating the bushing 55 by means of a radial stop pin 66 secured in the bushing nange 56 and extending through the semi-circular radial slot 40 in the inner housing 36 into a variable eccentric control collar 61. 61 is provided with a plurality of handles,l one 'o f which is shown at 68. Rotating the control collar 61 by means of the handle 68 will, through the stop pin 66,v rotate the eccentric bushing 55 and thus shift its center between its utmost limits inasmuch as the slot 40 extends 180. Dependcollar 61 isa stop pin 69 which extends into and has a path of travel along 10 in an adjusting and lock collar 1I, collar 1 I being suitably and adjustably secured as by set screws (not shown) to the top of the lower portion 4I of the inner housing 36.

At the end of the semi-circular annular'groove 10 in the collar 1I is a lock 12 consisting of a small cylinder having a radial slot 13 which may be aligned with the semi-circular groove 10 in the position shown in Fig. 3, permitting the stop pin 69 to be moved to the center of lock 12. The radial slot 13 forms the continuationrand the end of groove 10, when the handle 14 is projecting out from the collar 1I, 13 is radial of the longitudinal axis of ithe cylindrcal lock 12. `When in such central position, the lock 12 may be rotated 90 by means of its handle 14 which rits into a recess 14' adapted to receive it in the side of the lock collar 1I,` thus `preventing the stop pin 69 fromv leaving the same until the radial slot 13 has' again been aligned lwith the semi-circular groove in `the lock collar 1I. Below the lock collar 1I' there is located a coolant distributor 15 having a coolant inflow path 16 and a coolant outlet flow path 11'.` 'The coolant outlet flow path 11 is connected to a vertical passageway 18 in the lower portion 4I of inner housing 36 and is also connected to a conduit 80 supported by an adjustable fork 8| mounted by means of studs 82 on the outer housing I4. The coolant inlet path 16 connects to a similar and parallel passageway in the lower p01- tion 4I of the inner housing 36 and in turn is connected to a coolant supply conduit (not shown). Below the coolant distributor 15 there is threaded on the housing 36 aV lock nut and stop 83 and below this a regulating nut and stop 84. It will be noted that lock nut and stop 83 are each provided with countersunk packings 85 bearing against the coolant distributor 15 to prevent leakage therefrom. The extreme lower edge Vof lower portion ing 180 thereabout.

This control collar as illustrated. The slotl the lock collar 1I and the alip 86 eitendl to descend collar I5 and studs ter 6I to be drawn upwardly in a Additional explanation as to the manner in which the thread miller is preset may be thought desirable. `Ir it is desired to change the depth of thread or to compensate for cutter Wear, the thread miller is reset in the following manner. The set screws in lock collar 1i are loosened vso thatthe lock collar is free to rotate, and control collar 61 is rotated by means of handles 68 until the desired dimension is secured between the heel of lip 86 and the most remote cutting edge of cutter 6I. This dimension is usually measured with a micrometer. When the control collar 61 has been adjusted as above set forth, it is held in place'relative to the inner housing 36, and lock collar 1I is rotated relative toV control collar 61 until lock 12 engages the'stop pin 69. The lock collar 1I is then locked in this position by means of its set screws. Inthis manner it will be seen that lock 12 in lock collar 1I is so located as to engage and lock stop pin 69 at the exact de-sired point ofeccentricity,l and rotation of control collar 61 is permitted as farv as lthe diametrically opposite point of eccentricity for the purpose of withdrawing cutter 6I toward lip 86 for insertion 'into the hole. Then, afterthe'cutter is rotating,

rotation of control collar 61 until stop pin 69 engages lock 12 will result in the cutter 6I achieving the exactdepthci cut desired.l The thread miller I0 is attached to a radial' drill press or any suitable portable drillhead by means ci the split I6 and the press spindle I1 is thus connected to the taper sleeve adaptor I3. The plate I2 and thread miller I0 are placed in relative position so that the inner housing rest lip can enter to the bottom I3' of a previously drilled cylindrical hole I3. Before the milling cutter 6I can be extended to the bottom o the hole, however, it must be withdrawn within the diameter ofthe lip 86 by releasing the stoppin 69 from the vlock 12 and'then rotating the handle 68. This will cause the eccentric bushing to rotate 180 and Change the eccentricity of the cutter shaft 58 relative to the drive shaft 2I. The handwheel 50 is thenrotated causing ythe inner housing 36 until the lip 86' abuts the bottom I3 of the previously drilledv hole. The power is then turned on and is transmitted by means of the splines 20, drive shait'ZI, coupling shuttle 60 and cutter shaft 58 to the cutter 6I Handle 68 is then rotated while the cutter 6I is operating -until the handle 68 has brought the stop pin 69 to the end of the annular groove 10 yand into look 12 whereupon the lock handle 14 is rotated to lock it therein'.v At this time, the cutter 6I will have moved radially to its limit of eccentricity as vit'V has out its way into the side of 'the hole in the plate I2. `Then as 'the cutter 1I continues in rotation, handwheel 50 will be slowly rotated in the opposite direction causing the cutn spiral path determined b-y the cooperating acme threads 38 and 53, thus cutting the internal thread I I in the plate I2 as it does so. Due to the fact that cutting commencesrat the bottom of t'l'iev hole and advances upwardly,A the chips merely collect at the bottom without interfering with the operation. a suitable coolant being provided through the coolant distributor 15l andthe vertical passageways in lower portion 4 I of inner housingl 3 6.

the Y Other modifications and ber and arrangement of those skilled in the art without departing from the nature of the invention, within the scope of what is hereinafter claimed.

The invention described herein may be manufactured and used by or for the Government of the United States of America" for governmental purposes without 'the payment ofany royalties 'thereon or therefor. Y

What is claimed is:

1. A thread miller comprising an outer housing, a power shaft in said housing, a drivesh-aft splined to said power shaft, an inner housing journalled abou-t said drive shaft, said'inner'housing including a concentric .cylidrical upper portion having an interrupted external thread extending about part of said upper portion, a depending lower portion having an eccentric cylindrical internal shaftway therethrough, a driven shaft, an eccentric bushing in which said driven shaft is journalled, said eccentric bushing being rotatable within said eccentric portion of said inner housing, a coupling shuttle connecting said drive shaft to said driven shaft, a milling cutter mounted on said driven shaft, means connected to said eccentric bushing for rotating the same and'thus varying the eccentricity of said milling cutter, means for locking said milling cutter in radially changes in the numextended position, means for spirally m-oving saidv inner housing lto cause said milling cutter to mill a thread in a previously drilled hole in a plate, and means for guiding said inner housing in the drilled hole in a plate extending partly around its edge.

2. A thread miller comprising an outer housing, a power shaft in said housing, a drive shaft splined 'to said power shaft, ,an inner housing J'ournalled about said drive shaft, said inner housing including a concentric cylindrical upper lpor- -v tion having an interrupted external thread extending about part of said upper portion, a depending lower portion having an eccentric cylindrical internal shaftway Ytherethr'oug a driven shaft, an eccentric bushing in which said driven shaft is journalled, said eccentric bushing being rotatable within said eccentric portion of said inner housing, a coupling shuttle connecting said drive shaft to said driven shaft, a milling cutter mounted on said driven shaft, means connected to said eccentric bushing for rotating the same and thus varying .the eccentricity of said milling cutter, means for locking said milling cutter in radially extended position, means for spirally moving said inner housing to cause said milling cutter to mill a thread in a previously drilled hole in a plate, and means for guiding said innel housing inthe drilled hole in a plate.

3. A thread miller comprising an outer housing,

a power shaft in said housing, a drive shaft' splined .to said power shaft, an inner housing journalled about said drive shaft, 'said inner housing including a concentric cylindrical upper portion having an interrupted external thread extending about part of said upper portion, ya depending lower portion having an eccentric cylindrical internal shaftway therethrough, a driven shaft, an eccentric bushing in vwhich said driven shaft is lournalled, said eccentric bushingV being rotatable within said eccentric portion of said inner housing, a coupling shuttle connecting said drive shaft to said driven shaft, a milling cutter mounted on said driven shaft, means connected to said eccentric bushing for rotating the same and thus varying the eccentricity of said millthe parts may be made by comprising a vdepending lip a semi-circular radi-al said drive shaft to ing cu-tter, said bushing rotating meanscomprisling a control collar about said inner housing and a stop pin extending from said bushing through slot insaid inner housing into said control collar, means for locking said milling cut-ter in radially Vextended position, means for spirally moving said inner housing to cause said milling cutter to mill a thread ina previously drilled hole in a plate, and means for guiding said inner housing in the drilled hole in a plate.

4. A thread miller comprising an outer housing, a power shaft in said housing, a drive shaft splined to said power shaft, an inner housing journalled about said drive shaft, said inner nous Ving including a concentric cylindrical upper p0rtion having an interrupted external thread ex- 'tending about part of said upper portion, adepending lower portion having an eccentricl cylindricalv` intern-al shaftway therethrough, a driven shaft, an eccentric bushing in which said driven shaft is `iournalled, said eccentric bushing being rotatable within said eccentric portion of said inner housing, l

drive shaft to said driven shaft, a milling cutter mounted on to saidA eccentric bushing for rotating the same and thus varying the eccentricity of said milling cutter, means forlocking said milling cutter in radiallyV extended position comprising a locking collar adjacent -said control collar, an annular groove in said locking collar, a stop pin extending from said control collar into said'locking'collar semi-'circular annular groove, a stop pin lock at one end of said semi-circular annular groove consisting of la rotatable cylinder having a ra-v dial slot adapted to be aligned and misaligned with said semi-circular annular groove and a handle for rotating said cylindrical loci: from 4aligned unlocked position to misaligned locked position, means for spirally moving said inner housing to cause said milling cutter to mill a thread in a previously drilled hole in a plate, and means for guiding said inner housing in the drilled hole in a plate. f

5; A thread miller comprising anouter housing, a power shaft in said housing, a', drive shaft splined to said power shaft, an inner housing journalled about said drive shaft, said inner housing including a concentriccylindrical upper portionhaving an interrupted external thread extending about part lof said upper-portion, a depending lower portion having an eccentric cylindrical internal shaftway therethrough, a driven shaft, an eccentric bushing in 'which said driven shaft is journalled, said eccentric bushing being rotatable within said eccentric ,portion of said inner housing, a coupling shuttle connecting said driven shaft, a milling cutter mounted on saidvdriven shaft, means convmilling cutter,

drilled hole in a nected to said eccentric bushing for rotating the same and thus rvarying the eccentricity of said means for locking said milling cutter .in radially extended position,` means for spirally moving said inner housing to cause said milling cutter to mill a thread, in a previously plate, said spirallymoving means comprising a' worm wheel in said outer housing having a two diametered aperture about said interrupted thread portion of said inner housing and a lead thread guide nut secured to saidouter housing, said lead thread guide nut being internally threaded corresponding to the threads of the thread portion of said inner housing and means for rotating said worm wheel to rotate said inner housing and thereby cause said inner a coupling shuttle connecting said said driven shaft, means connected s rprising a Worm outer housingfand means for controllably rotating saaidwormrshafufand means Aforfguiding said inner hmising'in the drilled hole in a Aplat-e.

Vva thread in a .previously drilled hol'ein a Y a power shaft in said housing, a

ausi-,asv

guidenut, said l.worm wheel .rotating means comshaft `extending through said 6. tAthread :miller comprising vaniouter housing, a powershaft insaid housing, a drive shait'splined io said power shat, an inner lhousing journalled about eaiddrive shaft, said inner housing including a concentric cylindrical upper portion having an interrupted external thread extending about part 'of said upper portion, aV depending lower portion having an eccentric cylindrical internal shaft-way therethrough, a tric bushing in which said driven shaft is journalled, said eccentric Ybushing being 4rotatable within said eccentric portion'of said inner housingga coupling shuttle connecting said drive shaft tosaid driven shaft, a Amilling cutter mounted on .saiddrivenrshaft,.means 'connected to said eccentric bushing for rotating the same and thusvary` ling the eccentricity of said milling cutterfmeans Yfor locking fsaid milling cutter in radially Vextended position, means for -spirally moving said inner housingto cause said milling 'cutter to'milla thread in a previously drilled hole VVin a plate, means for guiding said yinner housing in the drilled hole in a pla-te comprising a depending lip extending partly around its edge, .and cutter coolant supply .means including coolantinlet and outlet passageways extending through .the eccentric portion of said inner housing towithin said depending lip, and a `coolantcollar having coolant .paths connected to said housing passageways and reconduit coolant supply means. l Y

7. A thread miller comprising an outer housing, a powershaft in said housing,.a drive shaft .splined to said power shaft, an inner housing journalled vabout said drive shaft, said inner housing including aconcentric'cylindrical upper portion having an interrupted external thread .extendingjabout part of said upper portion, a depending lower portion having an eccentric cylindrical internal shaftway therethrough, a driven shaft,an eccentric bushing in which said driven `shaft .is journalled., said eccentric bushing being rotatable Within said eccentric portion of said innerv housing, a coupling shuttle connecting said driveshaft to V.said driven shaft, a milling cutter mounted on said driven shaft, means connected to said eccentric bushing for rota-ting the same thus varying the eccentricity of tended position, means for spirally moving said inner housing to cause said millingcutterto .mill

'plaie andmeans for .guiding said inner housinginthe drilled hole in a plate ycomprising a depending y lip extending partly arounditsfedge, vsaid milling cutter being adapted to be retracted to within the external diameter of said depending 'lipjat one limit of eccentricity and to a milling position with a portion of said cutter beyond the diameter of said lip `at the other limit of eccentricity.

8. Athread miller comprising an outer housing, drive shaft splined to said power shaft, an inner housing journalled about said drive shaft, said inner housing including a concentric cylindrical upper-portion having an interrupted external thread extending about driven shaft, an eccen` said milling cutter, means for locking said milling cutter in radiallyex-v 'portion' having an leccentric T8 vpart; of saidgupper '.portionfa rd ep e ,nding lower cylindrical internal shaftway therethrough, a'driven shaft,-an eccen- 'tric bushing .in which said driven shaftis journalled, said eccentric bushing rbein-g .rotatable Within ysaid eccentricjpor-tion Vof said inner `hous- 1ing,a=coupling shuttleconnecting said drive shaft .to-said driven shaft, a milling cuttermounted -on-:said'd-riven shaft,-means connected tosaid eccentric bushing for rotating the same and thus varying the eccentricity oi" said milling cutter, said bushing rotating .means comprisingffa control coll'anabout said 4inner housing ,and a-stop pin .portion of said' inner for` ,guiding ,said inner in aplate comprising a ofeccentricity and llip at the other limit of eccentricity.

extending from -said bushing through .a semi- -circular radialzslot insaid-innerrhousing :into said Acontrol collar, means .for ,locking said Vmilling cutter in radially extended-,position comprising a locking collar adjacent said control collar, .an

'annular groove .in .said locking collar, a stop .pin

extending .from said control collarinto said loci;- ing-collar semi-circular annular groove, and a stop pin: lock at .one end ci said semi-circular annular groove .consisting of a rotatable cylinder havingfa radial slot adaptedto be aligned iand Vmi aligned withsaid `semi-circular annular `groove .and .a handle 4.for .rotating said cylindricalloc iroinaligned unlocked position. tomisaligned i `locked position, means .iorvspirally moving said -innerhousing to causesaid milling cutter to mill athread infa previously. drilled hole in va plate,

-saidspira-lly moving means comprising a vworm wheel in said outer 'housing having a ytwo diam eteredfaperturel about saidinterrupted thread housing and va lead thread guide nut secured to said louter housing., said leajd .thread guide nut being Ainternally threaded corre- ,spondingto the threads of the thread portion of said inner .housing andmeans for rotating said worm Wheel to .rotate said inner housing. and thereby .cause -said innerhousing to move. spirally through said lead .thread extending through said .outer housing and means forcontrollably vrotating said worm shaft, means housing in the drille'dhole depending lip. extending partly around its edge and cutterV coolantsupply to within said depending lip, K coolant paths con nected to said housingpassageways and to con,-

' v duitcoolant supply means, lsaid milling 'cutter being adapted to be retracted to within theexternal diameter of said depending lip at onelimit I. to a milling position with a portion of said cutter beyond the diameter of said FREDERICK .1. KRATCHMN.

REEERENCESCITED I The following references Aare of record inthe me of this patent: Y Y

PATENTS UNITED STATES Number yName Date 472,126. Johnson i Api.' 5, 1892 1,316,718 .Ha11- sept. 23,1919 1,403,555 .101151 Jan, 17, 1922 ,1,430,933 Brandt et a1; oem, 1922 yvvoodcoei; July 18,1933

.guide nut, said worm` `wheel rotating means comprising aY Worm shaft 

